Some of the key aspects affecting analysis of a rough surface are described in Fig. 1. If a hypothetical sample consisting of 96% Si, 1% O, 1% Na, 1% Al and 1% Fe is analysed at 20kV at constant beam current with an x-ray detector elevated at 30deg from horizontal then the measured intensities of the various characteristic lines will vary with tilt. While absorption of low energy x-rays is reduced as the sample tilts towards the detector, there is also a gradual loss of intensity due to increased backscatter. At the lower beam voltage of 5kV, absorption of x-rays at zero tilt is already small and Fig.2 shows that variation in intensity with positive tilts is substantially reduced, although absorption still becomes significant if the sample is tilted away from the detector.